I just purchased Universe Sandbox today on steam. it peaked my interest as I never heard of it until earlier today. Not knowing what to do or where to start, I checked out the "Fun things to do" section. It walked me through the process of determining how long it takes light to travel from the earth to the moon.
During this process, I clicked something that I shouldn't cause the planets in the solar system went spiraling out of control and the moon just made a B-line in the oposite direction.
I don't know how I did it, but I like what I did. I think this games gonna entertain me for a long time.